Conventionally, there has been known a centrifugal compressor that is provided between an impeller and a scroll, and provides diffuser vanes which carry out slowdown pressurization of the fluid speeded up by the impeller, on a diffuser path. As the modification of such a centrifugal compressor, there is a suggestion in which the vanes are provided on both of a hub side wall surface and a shroud side wall surface composing the diffuser path, and vanes provided on the shroud side wall surface are rotated coaxially with a rotating shaft of the impeller (See Patent Document 1). This suggestion changes a relative position relationship between the vanes provided on the hub side wall surface and the vanes provided on the shroud side wall surface in order to improve the efficiency of the centrifugal compressor.